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Ultrasonic Acoustic Deterrents (UADs)

There’s some evidence to suggest that bats, at least some species, are attracted to wind turbines, but what that is, if anything beyond sheer curiosity, remains unknown.

One promising solution Bat Conservation International’s wind program team, under the auspices of the BWEC, is investigating the effectiveness of Ultrasonic Acoustic Deterrents, or UAD devices, mounted on the wind turbines themselves.

The idea is that these devices will “jam” bats’ echolocation or make the airspace around the turbine aurally uncomfortable, thereby keeping bats away from potential dangerous rotating turbine blades. Researchers got the idea from some species of moth's ability to "jam" bat calls in order to avoid predation.

Ultrasonic Acoustic Deterrents (UADs) are devices that emit a loud, high frequency noise (sound human can’t hear) - and that bats will avoid. It is hypothesized that placing UADs on wind turbines may allow wind energy facilities to operate normally while dramatically decreasing bat fatalities.

The tricky thing is to produce a robust device that can withstand being exposed to the environmental conditions experienced 80 to 100 m above ground level, and be effective at deterring bats away from large rotor-swept areas of current and future turbines. Field trials have shown promise but testing on operating turbines provide technological and logistical challenges that are currently being refined. If proven, UADs could provide an alternative impact reduction strategy that is more cost effective than operational minimization allowing wind turbine operators more options to reduce impacts to bats.

Field tests are still under way to determine how well the devices perform under various environmental conditions, how effective they are compared to operational minimization and which species can be deterred by the devices mounted on to of operating wind turbines.

BCI is planning three studies in 2017 to investigate the effectiveness of a UAD-designed and manufactured by Renewable NRG Systems (RNRG). One of these, funded by the U.S. Department of Energy, will compare the reduction levels of the deterrents with operational minimization, specifically feathering blades to 5.0 m/s (or 2.0 m/s above the preset operating conditions). Moreover, we will combine both impact reduction strategies to determine whether there is an additive effect, furthering the reduction in bat fatalities.

Preliminary functionality tests of the RNRG deterrent, conducted in 2016, showed significant improvements over previous generations of the technology. The devices passed all reliability tests, both in the lab and when installed on wind turbines, and showed no water entry or overheating (both issues commonly experienced in the previous design). During ground-based tests of the device, we documented a significant reduction in bat activity in areas of high bat concentrations (e.g., ponds where bats drink and forage for insects).